3 files changed, 41 insertions, 27 deletions

diff --git a/modules/audio_processing/audio_buffer.cc b/modules/audio_processing/audio_buffer.cc
index 1ceba383..fb2c200e 100644
--- a/modules/audio_processing/audio_buffer.cc
+++ b/modules/audio_processing/audio_buffer.cc
@@ -70,8 +70,9 @@ void StereoToMono(const int16_t* left, const int16_t* right, int16_t* out,
 // One int16_t and one float ChannelBuffer that are kept in sync. The sync is
 // broken when someone requests write access to either ChannelBuffer, and
 // reestablished when someone requests the outdated ChannelBuffer. It is
-// therefore safe to use the return value of ibuf() and fbuf() until the next
-// call to the other method.
+// therefore safe to use the return value of ibuf_const() and fbuf_const()
+// until the next call to ibuf() or fbuf(), and the return value of ibuf() and
+// fbuf() until the next call to any of the other functions.
 class IFChannelBuffer {
  public:
   IFChannelBuffer(int samples_per_channel, int num_channels)
@@ -80,19 +81,24 @@ class IFChannelBuffer {
         fvalid_(true),
         fbuf_(samples_per_channel, num_channels) {}
 
-  ChannelBuffer<int16_t>* ibuf() {
+  ChannelBuffer<int16_t>* ibuf() { return ibuf(false); }
+  ChannelBuffer<float>* fbuf() { return fbuf(false); }
+  const ChannelBuffer<int16_t>* ibuf_const() { return ibuf(true); }
+  const ChannelBuffer<float>* fbuf_const() { return fbuf(true); }
+
+ private:
+  ChannelBuffer<int16_t>* ibuf(bool readonly) {
     RefreshI();
-    fvalid_ = false;
+    fvalid_ = readonly;
     return &ibuf_;
   }
 
-  ChannelBuffer<float>* fbuf() {
+  ChannelBuffer<float>* fbuf(bool readonly) {
     RefreshF();
-    ivalid_ = false;
+    ivalid_ = readonly;
     return &fbuf_;
   }
 
- private:
   void RefreshF() {
     if (!fvalid_) {
       assert(ivalid_);
@@ -266,69 +272,71 @@ void AudioBuffer::InitForNewData() {
 }
 
 const int16_t* AudioBuffer::data(int channel) const {
-  return channels_->ibuf()->channel(channel);
+  return channels_->ibuf_const()->channel(channel);
 }
 
 int16_t* AudioBuffer::data(int channel) {
   mixed_low_pass_valid_ = false;
-  const AudioBuffer* t = this;
-  return const_cast<int16_t*>(t->data(channel));
+  return channels_->ibuf()->channel(channel);
 }
 
 const float* AudioBuffer::data_f(int channel) const {
-  return channels_->fbuf()->channel(channel);
+  return channels_->fbuf_const()->channel(channel);
 }
 
 float* AudioBuffer::data_f(int channel) {
   mixed_low_pass_valid_ = false;
-  const AudioBuffer* t = this;
-  return const_cast<float*>(t->data_f(channel));
+  return channels_->fbuf()->channel(channel);
 }
 
 const int16_t* AudioBuffer::low_pass_split_data(int channel) const {
   return split_channels_low_.get()
-      ? split_channels_low_->ibuf()->channel(channel)
+      ? split_channels_low_->ibuf_const()->channel(channel)
       : data(channel);
 }
 
 int16_t* AudioBuffer::low_pass_split_data(int channel) {
   mixed_low_pass_valid_ = false;
-  const AudioBuffer* t = this;
-  return const_cast<int16_t*>(t->low_pass_split_data(channel));
+  return split_channels_low_.get()
+      ? split_channels_low_->ibuf()->channel(channel)
+      : data(channel);
 }
 
 const float* AudioBuffer::low_pass_split_data_f(int channel) const {
   return split_channels_low_.get()
-      ? split_channels_low_->fbuf()->channel(channel)
+      ? split_channels_low_->fbuf_const()->channel(channel)
       : data_f(channel);
 }
 
 float* AudioBuffer::low_pass_split_data_f(int channel) {
   mixed_low_pass_valid_ = false;
-  const AudioBuffer* t = this;
-  return const_cast<float*>(t->low_pass_split_data_f(channel));
+  return split_channels_low_.get()
+      ? split_channels_low_->fbuf()->channel(channel)
+      : data_f(channel);
 }
 
 const int16_t* AudioBuffer::high_pass_split_data(int channel) const {
   return split_channels_high_.get()
-      ? split_channels_high_->ibuf()->channel(channel)
+      ? split_channels_high_->ibuf_const()->channel(channel)
       : NULL;
 }
 
 int16_t* AudioBuffer::high_pass_split_data(int channel) {
-  const AudioBuffer* t = this;
-  return const_cast<int16_t*>(t->high_pass_split_data(channel));
+  return split_channels_high_.get()
+      ? split_channels_high_->ibuf()->channel(channel)
+      : NULL;
 }
 
 const float* AudioBuffer::high_pass_split_data_f(int channel) const {
   return split_channels_high_.get()
-      ? split_channels_high_->fbuf()->channel(channel)
+      ? split_channels_high_->fbuf_const()->channel(channel)
       : NULL;
 }
 
 float* AudioBuffer::high_pass_split_data_f(int channel) {
-  const AudioBuffer* t = this;
-  return const_cast<float*>(t->high_pass_split_data_f(channel));
+  return split_channels_high_.get()
+      ? split_channels_high_->fbuf()->channel(channel)
+      : NULL;
 }
 
 const int16_t* AudioBuffer::mixed_low_pass_data() {
diff --git a/modules/audio_processing/audio_buffer.h b/modules/audio_processing/audio_buffer.h
index 5c26ae29..acf5753c 100644
--- a/modules/audio_processing/audio_buffer.h
+++ b/modules/audio_processing/audio_buffer.h
@@ -55,7 +55,9 @@ class AudioBuffer {
   int samples_per_split_channel() const;
   int samples_per_keyboard_channel() const;
 
-  // It can be assumed that channels are stored contiguously.
+  // Sample array accessors. Channels are guaranteed to be stored contiguously
+  // in memory. Prefer to use the const variants of each accessor when
+  // possible, since they incur less float<->int16 conversion overhead.
   int16_t* data(int channel);
   const int16_t* data(int channel) const;
   int16_t* low_pass_split_data(int channel);
diff --git a/modules/audio_processing/common.h b/modules/audio_processing/common.h
index 10249cc2..98e36cb0 100644
--- a/modules/audio_processing/common.h
+++ b/modules/audio_processing/common.h
@@ -54,10 +54,14 @@ class ChannelBuffer {
   }
 
   T* data() { return data_.get(); }
-  T* channel(int i) {
+  const T* channel(int i) const {
     assert(i >= 0 && i < num_channels_);
     return channels_[i];
   }
+  T* channel(int i) {
+    const ChannelBuffer<T>* t = this;
+    return const_cast<T*>(t->channel(i));
+  }
   T** channels() { return channels_.get(); }
 
   int samples_per_channel() { return samples_per_channel_; }